Field
The present disclosure relates generally to an apparatus and method for the processing of molten glass, and more particularly an apparatus and method for conveying molten glass from a delivery vessel to a forming body.
Technical Background
The fusion glass making process is known for producing high quality glass sheets of extraordinary thinness without grinding or polishing to further thin the as-drawn glass. The process in its simplest form comprises flowing molten glass over two opposing and converging sides of a forming body, wherein the separate flows of glass meet at a bottom edge of the forming body to form a glass ribbon. The glass ribbon cools to an elastic state, after which the ribbon can be cut into individual glass sheets.
Recently, strengthened glass has become popular as cover glass to protect electronic devices such as cell phones and tablet computers. Such glass is typically chemically strengthened by ion-exchanging the surfaces of the glass. However, ion-exchanging does not readily lend itself to an in-line process, and therefore becomes an expensive batch process requiring multiple steps. Moreover, the chemicals used in the ion exchange process must be properly handled to comply with environmental constraints, further adding to the expense. Applications that would otherwise benefit from strengthened glass, such as glass cover plates for household appliances, e.g. refrigerators, may not warrant the expense of ion-exchanged glass. Thus, a process for producing low-cost strengthened glass in thin sheets and in a continuous process addresses a beneficial need. To that end, in-line lamination processes have been developed wherein multiple flows of glass are combined to form a laminated glass ribbon. Preferably, the laminated glass ribbon comprises two different glasses with two different coefficients of thermal expansion such that when the glasses cool, the outer layer of the glass ribbon is in compression and subsequent glass sheets cut from the ribbon are capable of resisting damage better than a glass sheet originating with a single-layer ribbon.